This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project investigates the roles of specific opioid and dopamine receptor mechanisms in the dual abuse of cocaine and opioids to provide an objective framework for identifying receptor targets for the pharmacological management of speedball abuse.